[Medical Q&A] What would happen if food lost its “freshness”?

Author: Li Haijie, Associate Professor, School of Public Health, North China University of Technology

Reviewer: Yan Shengguang, Professor of School of Public Health, North China University of Technology

When food goes from fresh to spoiled, it is a process in which microorganisms use the nutrients in food to grow and multiply in large quantities, which not only reduces the nutritional value of food, but also produces various metabolic products that are harmful to the human body. When food is spoiled, it can generally be seen from its appearance, mainly including the following three types of changes.

1. Color change. Green vegetables may turn yellow, and some fruits and meat may become darker or lighter. When rotting and spoiling occurs, fruits may develop brown spots, and meat may turn dark green.

2. Changes in smell. Stale fruits have a very light or even no fruity aroma. Slightly rotten fruits will produce the smell of alcohol fermentation. Stale aquatic products and livestock and poultry meat will produce a foul odor, which is the smell of protein decay and decomposition by microorganisms. Histamine, cadaverine, putrescine, etc. produced by bacteria decomposing proteins in meat and meat products not only produce bad odors, but also cause food poisoning.

3. Texture changes. Fruits or vegetables first lose moisture, the skin or surface of the fruit or vegetable becomes wrinkled, and the whole thing wilts, then softens, becomes sticky, and begins to ooze juice, or even rots in the fruit or stems and leaves. Meat products begin to soften and lose elasticity, and the meat becomes sticky when it is spoiled.